Silane coupling agents are compounds which have on a single molecule both a moiety that is reactive with inorganic matter and a moiety that is fully reactive with and soluble in organic matter. Because such agents act as adhesive aids at the interface between inorganic matter and organic matter, they are widely employed as composite resin modifiers.
Many silane coupling agents and siloxane oligomers that are partial hydrolytic condensates thereof are compounds having two or more alkoxysilyl groups per organic functional group, whereas only a few are compounds having two or more organic functional groups per alkoxysilyl group.
As an example of the latter, Patent Document 1 discloses organic compounds containing two or more epoxy groups per alkoxysilyl group, wherein two glycidoxy groups and a trimethoxysilylpropyl group are attached to an aromatic ring.
However, the compounds of Patent Document 1 have a structure which, in terms of molecular design, makes it impossible to introduce three or more epoxy groups per alkoxysilyl group.
Patent Document 2 discloses compounds having three or more epoxy groups per alkoxysilyl group, wherein a plurality of glycidoxy groups and an alkoxysilyl group are attached to a polyglycerol skeleton or a sorbitol skeleton.
Yet, the compounds of Patent Document 2 are highly hydrophilic owing to the structure of the backbone and the nature of the plurality of urethane linkages, and therefore cannot be employed in coating and adhesive compositions where hydrophobic properties are required. Moreover, the structure of these compounds leads to marked declines in heat resistance, yellowing resistance and crack resistance.